Fungi are at present controlled in plants by applying synthetic inorganic or organic fungicides to the area to be treated. Such fungicides are costly and energy consuming in their production, and often they are not very effective in combating the fungi. This may often be due to climatic or environmental conditions prevailing in the area or time of application. Also, the use of a fungicide over a prolonged period of time tends to select for fungi which are tolerant to the fungicide. Most of the known fungicides being alien to the ecosystems wherein they are spread also tend to accumulate and eventually exhibit undesired side effects.
For these and other reasons it is desirable to develop biological fungicides that are easily digested or degraded in nature and do not consume the large amount of energy required for the chemical synthesis of most known fungicides.
The genus Cercospora is known worldwide as the cause of leaf spot diseases on a large number of hosts of different genera. Some species of Cercospora are known to produce different metabolites. For example, C. betiocola produces fulvic acid (Sakaki et al., Agric. Biol. Chem. 45(5):1275-1276 (1981)) and a yellow phytotoxin (Martin et al., Proc. Int. Bot. Congr. 13:296 (1981)).
C. kikuchii produces cercosporin (Matsueda, S., Takagaki, K., Shimoyama, M., and Shiota, A. Studies on fungal products. V. Antimicrobial aspects of Quinone derivatives and Yakugaku Zasshi 100(9): 900-902 (1980)) and ergosterol-5,8-peroxide (Matsueda, S., Shimoyama, M., Imaizumi, T., Tsushima, Y., Studies on fungal products 4. Biological effects of ergosterol-5,8-peroxide. Yakugaku Zasshi 102(4): 347-351 (1982)). Matsueda et al. found cercosporin to inhibit the growth of Staphylococcus aureus, Bacillus subtilis, Pseudomonas aeruginosa, E. coli and Candida japonica. Cercosporin has been isolated as red crystals, Pfizer Handbook of Microbial Metabolites McGraw-Hill Book Co., Inc. N.Y. Toronto London from Shimpei Kuyama and Teiichi Tamura. J. Am. Chem. Soc. 79:5725-5726 (1957).
C. arachidicola produces an anthraquinonoid metabolite (Stoessl, A., Stothers, J. B., Minor anthraquinonoid metabolites of Cercospora arachidicola. Can. J. Chem. 63(6): 1258-1262 (1985)), and C. cruenta produces metabolites structurally related to abscisic acid (Takayuki Oritani, Kyohei Yamashita. Isolation and structure of 4'-hydroxy-.gamma.-ionylidene acetic acids from Cercospora cruenta, a fungus producing (+) -Abscisic acid. Agric. Biol. Chem. 51(1): 275-278 (1987)), such as mutasteine (Japanese Patent No. 48920 issued 861027). C. rosicola produces abscicic acid (Japanese Patent Application No. 192674 filed 8211102).
C. fusimaculans has been isolated from a number of grasses (Ellis, M. B., More dematiaceous Hyphomycetes. Commonwealth Mycological Institute, Kew, Surrey, England (1976)) and has been reported to cause foliar disease or sorghum spp. (Wall, G. C., Mughogho, L. K., Frederiksen, R. A., Odvody, G. N. Foliar disease of sorghum spp. caused by Cercospora fusimaculans. Plant Dis. 71(8): 759-760 (1987)) and Bajra Pennisetum typhoides (Patel, K. S. A. Cercospora fusimaculans leaf spot disease of Bajra Pennisetum typhoides in Gujarat. Curr. Sci. (Bangalore) 42(1): 34). So far there has been no recording of C. fusimaculans producing a fungicidally active principle.